A) Field of Invention
The present invention relates to a device for improving the shielding effectiveness of an Electromagnetic Interference (EMI) enclosure and, more particularly, to a device for improving the shielding effectiveness of an aperture in the enclosure which is used for mounting an electrical component.
B) Description of Related Art
FIG. 1 shows a cross-sectional side view of a conventional enclosure 1 which houses sensitive electrical components. The enclosure 1 typically includes two types of electrical components--electrical components 3 which are used to process information, and electrical components 7 which are used to display information or to control processing functions.
The electrical components 3 contained within the enclosure 1 are typically attached to a stationary surface 2, such as a printed circuit board, and can be used for any operation. However, for purposes of this discussion, it is assumed that the electrical components 3 are used on an aircraft to process information received from either an air traffic control station or another aircraft.
The enclosure 1 also includes electrical components 7 which are used for displaying information or control processing. The electrical component 7 is positioned within an aperture 5 defined in an outer surface of the enclosure 1. The electrical component 7 contains threads 8 on its outer surface and therefore can be secured to the enclosure 1 by use of a nut 9.
Conventional enclosures, such as the one shown in FIG. 1, are typically made of a metal to shield the electrical components 3 from unwanted EMI. However, conventional enclosures fail to maintain an adequate EMI shield. Two factors contribute to this failure.
The first factor relates to an infiltration caused by an external EMI 11 which is present in the environment surrounding the enclosure 1. This external EMI 11 is generated by either natural events, such as lightning, or by other man-made electrical devices located on or near the plane.
The external EMI 11 enters the enclosure 1 in a number of ways. For example, when the electrical component 7 is not shielded, the external EMI 11 can enter the enclosure 1 by simply passing through the aperture 5. The EMI 11 can also enter the enclosure 1 through the conductive elements 6 contained within the electrical component 7.
When the external EMI 11 infiltrates the enclosure 1, the operation of the electrical components 3 are susceptible to operational degradation.
The second factor contributing to the failure of conventional enclosures results from an internal EMI 13 produced by the electrical components 3 themselves. This internal EMI typically represents electromagnetic emissions from signal leads, power leads, or antenna leads contained on the electrical components 3. The internal EMI can escape the enclosure 1 and interfere with other electronic devices outside of the enclosure.
In view of these problems with conventional enclosure openings, there currently exists a need for a device which (i) can improve the shielding effectiveness of apertures for electrical components placed within an enclosure, (ii) can easily be installed on the enclosure, and (iii) can be manufactured with low cost materials and low cost manufacturing techniques.